1. Field of the Invention
This invention relates to high dynamic range (HDR) imaging, and in particular, it relates to selection of a subset from a set of images of different exposure levels for creating an HDR image.
2. Description of Related Art
High dynamic range (HDR) imaging is a technique used in image processing and digital photography to handle sources that have extremely large ranges of brightness (light intensity). For example, an outdoor scene in daylight may include blue sky and sunlit objects as well as objects in shadows; a night scene may include neon lights and brightly lit objects as well as poorly lit objects; an indoor scene may include bright windows as well as darker areas, etc. These scenes pose a challenge for imaging devices such as digital cameras; the dynamic range of the image sensor of currently available digital cameras often cannot adequately image such scenes. If the exposure level is adequate for capturing details of darker areas of the scene, the brighter areas will often be overexposed with details lost; conversely, if the exposure level is adequate for capturing details of brighter areas of the scene, the darker areas will often be underexposed with details lost.
HDR imaging techniques deal with this problem by taking multiple images of the same scene at various exposure levels, and then digitally merging the multiple images to create an HDR image that contains information from the original multiple images, so that details in both brighter and darker areas are adequately expressed in the HDR image. Methods for creating an HDR image from multiple images are generally known.
Bracketing is a technique in photography for taking multiple images of the same scene using different exposure levels or other different setting values such as focus, depth of field, etc. Some cameras can perform autobracketing, i.e., automatically changing the setting multiple times and take multiple images. Multiple images generated by exposure bracketing can be used to create HDR images.